1. Field of the Invention
The present invention generally relates to information recording apparatuses such as CD-R/RW drives and information recording methods, and more particularly to an information recording apparatus and method that prevents an occurrence of a buffer under-run.
2. Description of the Related Art
Japanese Laid-Open Patent Applications No. 10-293961 and No. 10-302387 each discloses an information recording apparatus that prevents an occurrence of a buffer under-run by adjusting a rate of writing information onto an optical disk through a buffer so that the writing rate is balanced with a rate of transferring data from a host computer to the buffer by controlling the number of rotations of a spindle motor in accordance with the data transfer rate through means for controlling the number of rotations of the spindle motor in accordance with an amount of data stored in the buffer. Here, the buffer under-run refers to an operation of interrupting data writing if the writing rate is higher than the data transfer rate so that the data stored in the buffer runs short and restarting the data writing after a predetermined amount of data is stored in the buffer. In this operation, the data writing is interrupted and restarted so that the continuity of the written data is maintained.
Such an information recording apparatus is capable of preventing the buffer under-run, and further realizes the maximum writing performance since writing is always performed at a rate close to that of transferring data from the host computer to the buffer. However, considering the response characteristic of the spindle motor or laser diode (LD) control, it is not easy to adjust the number of rotations of the spindle motor in accordance with the amount of data stored in the buffer whenever necessary.
That is, in the above-described information recording apparatus, since the spindle motor is slow in responding, the buffer is required to have a large capacity to accommodate a sudden change in the data transfer rate, thus resulting in pushing up the production costs. Further, the information recording apparatus stops a writing operation if a data transfer from the host computer is suspended for a certain period of time.
Moreover, the above-described information recording apparatus, which requires the LD control and an encoder circuit for analog adjustment of the writing rate, cannot be put into practical use with ease.
In order to solve the above-described problems, Japanese Laid-Open Patent applications No. 10-49990 and No. 2000-40302 each discloses an information recording apparatus that prevents an occurrence of a buffer under-run error by pausing writing of data and restarting the writing when the data is stored in the buffer.
Such an information recording apparatus is capable of preventing an occurrence of the buffer under-run error with no problem even if there is a great fluctuation in the rate of transferring data from the host computer or the data transfer is suspended for a certain period of time.
Further, the capacity of the buffer can be kept small since there is no need to take precautions against occurrence of the buffer under-run.
However, under conditions without occurrence of the buffer under-run error, a conventional information recording apparatus such as any of the above-described information recording apparatuses normally performs writing at the maximum writing rate, and repeatedly pauses writing of even a buffer-capacity amount of data, more or less, if the data transfer rate is a little lower. The conventional information recording apparatus has its writing performance deteriorated by overhead needed thereby.
Reduction of the buffer capacity lowers the costs of components of the information recording apparatus, but at the same time, increases the number of times the information recording apparatus pauses writing to deteriorate its writing performance. That is, there is a tradeoff between the cost reduction and the recording performance in the conventional information recording apparatus.
Further, when writing is paused and restarted, a loss of data may be caused depending on control accuracy. This may not lead to a fatal error, but may deteriorate recording quality to some extent compared with writing without pause and restart.
Therefore, some of users in quest of the highest recording quality hate to pause writing.
Furthermore, since the conventional information recording apparatus decreases its writing rate to prevent an occurrence of the buffer under-run, the conventional information recording apparatus has its writing performance all the more deteriorated in the case of a sudden occurrence of the buffer under-run due to heat calibration performed by an HDD or a temporary increase in a load on a CPU caused by another application.